Telephonic relay.



1 1111111121) MAR. 6, 1906.

J. TROWBRIDGE. TBL-EPHONIG RELAY. APPLICATION FILED JULY 14, 1906.

a sums-sum i.

PATENTED MAR. 6, 1906.

. J. TROWBRIDGE.

TELEPHONIO RELAY,

APPLIOATION FILED JULY 14, 1905.

' 5 SHEETS-SHEET z.

PATENTED MAR. 6, 1906.

No. 814,411. 1 J. TROWBRIDGE.

TELEPHONIG RELAY.

APPLIOATIOYN FILED JULY 14, 1905.

5 SHEETSSHEET 8.

PATENTED MAR. 6, 1906.

J. TROWBRIDGE. TELBPHONIG RELAY.

APPLIOATION FILED JULY 14, 1905.

5 SHEETS-11321 4.

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UNITED STATES PATENT OFFICE.

TELEPHONIC RELAY.

' No..ei4,4ii.

Specification of Letters Patent. 7 Applicatioi filed July 14,1905.Serial No 269.628.

Patented March 6, 190

To all whom it may concern:

Be it known that I, JOHN TROWBRIDGE,&

' citizen of the United States, and a resident of undulated.

Canibrid e, in the count of Hiddlesex and State of assa'chusetts, aveinvented new and useful Improvements in Telephonic-Re-- lays, of whichthe following is a specification. v My invention relates to the art oftransmitting electrical undulations; and its object is to so improve theconstruction of telephonic. relays or repeaters as to eliminate from thetransmitted undulations the disturbing influences which are manifestedaudibly at thereceiver in the form of crepitations which con'- fuse andsometimes suppress eiitirel the in- ,telligible articulations of speechw erewith the telephonic current is primarily excited or"Myimprovements, resently to be described in detail, are adaptab e tomany forms of telephonic relays and have demonstrated their capacity toeliminate the undesirable vibra-, tory and percussive disturbanceswherewith the operations of most telephonic relays have been impaired.-A descri tion of these improvements as they may e associated with oneform of telephonic rela will, however, suffice to instruct those skil edin the art in the essentials of their structure and operation so thatthey may be applied to othenforms of rela without the exercise of morethan the skil expected of persons trained in the practice of telephonyand the manufacture of telephonic instruments. 35

The difliculty which has heretofore attended the o eration of telephonicreceivers is attributab le in large measure to the practice of placingthe transmitter of the reliily u on or in direct contact with thereceiveriapliragm which is adjusted to the magnetic portion of thefield, thus loadin the dia hragm at the very point where loading has t emost detrimental eflect upon it. On the other hand,

in order to. transfer to the transmitter of the relay all the articulatevibrations of the receiver it'would seem that direct contact between thetwo was indispensable. I have discovered, in connection with testsandexperiments with telephonic relays, including the relay described in myUnited States Letters Patent No. 756,434, dated April 5, 1904, that thisseemin dead-lock can successfully be overcome an that the coexistence ina relay instrument of independent adjustability and intimatesound-transferring contact of t the transmitter and receiver is quitepossible conditions. y, t

In the drawings hereto annexed, Figures 1 2, 3, and 4 are illustrativeand explanatory of my invention; and Figs. to 10,1nclusive, show anembodiment thereof. Figs. 1 and 2 show diagrammatically an elementaryform.

of relay. Fig. 3 showsthe relay as applied to anfordinary telephonicreceiver. 1g. 4 illustrates the application of the elementary principleof Figs. 1 and 2 to a relay such as.

despite the seeming inconsistency of the two shown in my Patent N o. 756,434, dated April 5, 1904. Fi 5 is a lon itudinal elevation; Fig.6, avertical longitudinal section of an in strument which comprises acomplete embodiment of my invention. Fig. 7 is a ri ht-hand end, 8 aleft-hand end view, an Fi 9 a plan view, respectively,of Fig. 5; andFig. 10

is a detail showing the arrangement of reinforcin -magnets and thearmature associated therewith. Figs. 1 to 4, inclusive, are addressed tothe phase of the problem referable -to the difficulties heretoforeencountered by reasonof directfattachment of the transmitter to thereceiver in a telephonic relay. These figures do not illustrate a fullsolutio 't. but such part thereof aswill be illuminati in connectionwith the complete structure ii Fi s.5to 10.

eferring to Fig. 1, D represents the diahragm of a receiving instrument,which may e acoustically vibrated in consonance with the undulations ofarticulate speech. In'opposition to this'vibrator D there is mounted asupplemental vibrator, shown as a diaphragm D, which in this instance issecured to the end of a short cone R in such position as to receiveadvantageously the impact of aerial vibrations from the air in thepartiallyinclosed space G, whereby the two vibrators are separated. Onemember of a microphonic transmitter T is secured to or otherwise placedin mechanical contact with the vibrator -D, and the circuit C, withbattery B, is connected with the transmitter. members in the ordinarymanner, the coils I I of the usual induction-coil transferring theelectrical undulations to the line C, which roceeds to a distantreceiver. (Not shown in the drawings.) My researches and demonstrationshave, however, led me to prefer a form of relay wherein the twovibrators are separated by a much thinner gaseous intermediary thanthatsiiggested in Fig. 1. Thus in Fig. 2- the supplemental vibrator D isshown as a thin diaphragm (which should be circular in form) providedwith a flange or rim turned toward the receiver-diaphragm D; otherwisethe arrangement is substantially the same as that illustrated by Fig. 1.If we regard the diaphragm D, Figs. 1 and 2, as the diaphragm of atelephonic receiver and assume the instrument to be in operation, it isobvious that the transmitter T and the receiver may be independentlyadjusted and that the gaseous intermediary between the diaphragms D andD, being in free communication with the outside atmosphere, cannotassume a condition of pressure or tension which will impose an load orstress upon either diaphragm. Tl ie transmission of articulate speechfrom D to D will thus be free from disturbances such as attend thedirect attachment of a transmitter to a receiverdiaphragm; but theamplitude of the articulate vibrations will necessarily be materiallydiminished in transit from the receiver to the transmitter'and theresult in the transmittercircuit consequently enfeebled.

In Fig. 3 there is illustrated another mode of securing the benefits ofthe separation of the receiver-diaphragm from the transmitter-vibrator.The receiver-dia hra m D is mounted in the receiver-she R in the usualway. Secured to the lip L of the receiver the supplemental diaphragm Dis stretched across the central aperture of the said lip, and thetransmitter T is secured or otherwise telephonically connected to thecenter of the diaphragm D. In order to insure the freedom of the gaseouscushion G, which separates the vibrators D and D from the eiiectsofunbalanced pressure due to confinement and changes of temperature, Irecommend that one or two small apertures L be provided in the lip L.As'before, the transmitter connections to battery-circuit and line areas described with reference to Fig. 1. In the apparatus as shown in Fig.3 the intervention of the air-gap between the diaphragms D and vibratorD uite efieetively eliminates the disturbances no in other relays to thedirect contact between the receiver-diaphragm and the transmitter, whilethe solid intermediary provided by the ca L between the diaphragms D andD trans ers the mechanical vibrations to the transmitter T far moreeffectively than the air-gap alone, as in Figs. 1 and 2; but althoughthe solid connection illustrated in Fig. 3 is superior to thedisconnected arrangement of Figs. 1 and 2 it is nevertheless not allthat could be desired, for the reason that the insulating materials ofwhich the commercial receiver-case is composed is not ideally adapted tosound transference.

The forms of relay above described are not so constructed as toreproduce the electrical undulations of the receiver-circuit withenhanced force and amplitude in the transmitter or relay circuitand-arefor this reason doubtfully effective as relay instruments.Neverthe ess the local disturbances which occur in the transmitter andwhich (if the transmitter were connected directly to thereceiver-diaphragm D, as in sundry early forms of telephonicrelay)wouldreact upon the receiver undulations and produce the rattling andbuzzing noises which have in nearly all relay instruments impaired orobliterated the essential articulate character of telephonic undulationsare eliminated by the elasticintervening layer of air, which in theinstruments shown in Figs. 1 to 3, inclusive, separate the opposedarticulate undulations from the receivervibrator D to the supplementalvibrator D with unimpaired quality, and the'undulations transmitted in.the relay-line C C reproduce the articulate speech whereby the on inalsending instrument was excited.

n my United States Letters Patent Nos.

vibrators D and D.- This gaseous cushion, however, transmits'the'correctly 756,436 and 756,437 there are described a,

method and apparatus whereby telephonic undulations are repeated orrelayed from one circuit to another not only without loss in amplitudeand force, but with both these qualities enhanced. By means of themagnetically-balanced relay instruments shown and described in the saidpatents-the repetition of telephonic messages can recur indefinitely asadditional increments of electromechanical energy are supplied at eachstation, so that the stations are in truth relays. A full description ofthis method and apparatus is afforded by the specifications oi the saidLetters Patent.

In Fi 4 there is illustrated a mode of applying tIie air-gap connectionshown in Figs. 1 and 2 to a relay instrument of the character shown andescribed in Letters Patent No. 7 56,437 and particularly illustrated inFig. 5 thereof. In Fig. 4 hereto annexed, M.

receiving-line G" contains the armature-coil.

in circuit, and the undulations of current created in that line by adistant sending instrument react magnetically on the field of themagnets M M. Instead of securing the tran smitter T directly to the stemP, I secure it to the supplemental vibrator or diaphragm D, which, as inthe instruments shown in the previous Figs. 1 to 3, is separated fromthe vibrator D by an intervening cushion of free or normally inertgas-1n this case air. The:

form of supplemental vibrator is here shown as the same as that of Fig.2, and the transmitter connections to battery-cir uit, &c., are as inFi 1. Theefi'ect of th. balanced armature A- m the field of the magnetsM is to enhance the force. and effect of the undulations roduced in thecircuit C as these are transfiirred to the transmitter T. The effect ofthe gaseous cushion or layer G, as in the instruments shown in Figs.l'to 3, is to supress or absorb the reactionary crepitations liable tobe produced by the transmitter T. The intervention of the air-ga intheinstrument illustrated in Fig.4 has t e effect of preserving the,quality of articulate undulations, thoug it necessarily diminishestheir force and amplitude, and while this diminution is in partcompensated for by the peculiar mode of operation of the receivingportion of the relay shown it is obviously preferable to combine theadvantages of air separation with those of continuous solid contact, assuggested by Fig. 3. In all cases I believe it to be advisable tomaintain pressure balance as between the gaseous cushion and thecircumambient gas, so that there shall be no distortion of either of theop osed vibrators. ,It is also desirable to have the two vibrators quiteclose together and perfectly parallel as to their opposed surfaces.Concentric arrangement is obviously to be recommended.

In the Figs. 5 to 10, inclusive, there is shown an apparatus whichcombines the advanta es desirable: first, fromairap separation,wh1cheliminates disturbances due to load' on the receiver and preserves thequality of the articulations second, from solid continuous soundtransferring communication between the receiver and transmitter, and,third, from the enhancement of the force, and amplitude of the receivedundulations in and by the eculiar structure and 'mode of operation 0 areceiver such as shown and described in my pIatent aforesaid. Referringto the drawings, is a suitable base for the reception and mountin ofcontact-posts, and N 1s a standard rigid y secured to the base N-Slide-blocks N project from the rear of the standard N and en age theslides O, the slide-blocks N and sli es 0 bein dovetailed to establishtheir mutual slidin engagement. Differential screws 0, whic are threadedinto the slides O and slide-blocks N, control theadjustment of these twoparts. The ma nets M are securely clamped between the p ates O and Owhereof the former is rigidly secured to the slide 0. These parts areall infduplicate, the arts on either side carrying one of the reinorcingrelav-ma nets M. A block N, rig

. idly secured to the standard N, is central aipertured and threaded toreceive the shell between which and the block N 3 the susvtaming-diaphragm D is secured. Horizon-- tal posts N", secured to thestandard N, support the frame-plate Q1, which is provided with lugs Qand Q. e diaphragm D is se cured to a central aperture ln-the plate Q.

The stems P P are centrally fastened to the diaphragm D and D,respectivelg, and carry between them thqrectangular ame A, in which ismounted rhe armature A. This armature has its coil in circuit with atelephoneline, as described in m aforesaid atents. The dia hragms D and3 are referably constructed ofmica. In a circu ar shallow recess D,formed in the plate Q, there is secured the diaphragm D, wh1ch may be aplain plate of sheet-iron, such as used for commercial receiver-dia hrams. ,The diaphragm D constitutes t e vi rator for the transmitter T andis separated from. the diaphragm D of the receiver by an air-space, thedlaphra m f the receiver and transmitter vibrator ein opposed to eachother, preferably paralle and as close together as the convenienceofconstruction will allow. At or nearthe margin of the receiver-diaphragmD the ring Q is inserted, WhlCh serves in the 1nstance shown both as theclamp for the margin of the receiver-diaphragm and also as the solidcontinuous sound-transferring connection between the diaphragms D and D,the diaphragm D being brought into sufficient] continuous andintermittent contact wit the rin% fingers an K. The ring Q in order toobtain satisfactory results should be of metal and be brou ht intointimate contact with the receiver-diaphragm and thetransmittervibrator. consistent with a practically free ventilation ofthe air-s ace between the diaphragms D and D. T is free communicationbetween the air of the space between the diaphragr'ns and thesurroundingatmosphere is of value in that the pressure balance betweenthe inner space and the outside air precludes the production of stressesupon the receiver-diaphragm itself or upon the vibrator of thetransmitter, ifthat, as in the instance shown,

be also a continuous circular diaphragfii.

The diaphragm D, Fig. 6, is consldera larger in diameter than thediaphragm D, the effective diameter of the latter measured from theinside of the ring Q being somewhat less than half the diameter of theformer. The ring Q, bearing upon the peri hery of the diaphragm D, doesnot inte ere appreciably, probably not at all, with the responsivevibrations of the receiver-diaphragm D. This ring bears u on the largerdiaphragm D well within t 1e peri hery thereof, and consequently impartsto t e dia hra in D the vibrations manifested by tile iaphragm D, so asto make their efi'ectfelt emb means of the clamps or spring- Thiscontact, however, is not in-- 'IIO phatically at the center of thediaphragm'D,

whcreon the contact-point of the transmitter T is made to bear. thatthis proportionand arrangement of the Specifically, it is believedsound-transmitting parts is decidedl effect ive in transmitting thevibrations o the receiver-diaphragm to the transmitter Upon justingdevices results in what is in substance justing-bar is inwardly 3 springT The transmitter T is suspendedl upon a leaf-spring T, which is securedto the 1 upper end of theadjusting-bar T. This adinclmed at its lowerend T and the sloping surface of this inwardly-inclined artion isengaged by the end of an adjusting-screw Q wluch is threaded into'thelower lug of the plate Springclamps K K hold the diaphragm D in positionin the recess D. The magnets M have polepleces M, which slightly overlapeach other as viewed horizontally, Fig. 10, so that the ends of thearmature A lie between the overlapping pole-pieces M.

By means of the apparatus above de-' scribed the receiving andtransmitting'members of the relay are independently adjustable. Themagnets M are adjusted by means of the differential screws 0, which maybe operated singly or together, as desired, in order to produce aperfect balance of field around the armature A. The transmitter T, onthe other hand, is independently adjusted by means of the screw Q whichpresses the adjuster-bar T inward or allows 1t to swing outward underthe tension of the spring T The mode of hanging and pivoting these adaparallel-motion adjustment for the transmitter T, the radial action ofthe-spring T compensating for the radial action of the As I havehereinabove stated, in some of the telephonic relays heretoforeconstructed the contact-piece of the transmitter has been placed indirect contact with or has been secured to the diaphragm of thereceiver. This arrangement has stood in the way of the obtainment ofsatisfactory results, because the securement or contact of thetransmitter unduly loads the receiver-diaphragm and it is impossible tomake adjustments in the transmitter without undesirably affecting thereceiver. Moreover, all the disturbances and crepitationsdue to theoperation of the transmitter are directly transferred to the receiver,and the articulate speech originally transmitted by the line isconfused, or it may be wholly suppressed. By separating the vibratorwhich is in connection with the transmitter from the vibrating diaphragmof the receiver by a thin layer of air between the directly-opposedportions of the vibrator and diaphragm the consequences of too direct anintimate contact between the transmitter and the receiver-diaphragm areavoided, and either instrument may be adjusted independently of theother. Furthermore, by con structing the instrument so that thecommunication of vibrations from the receiver-diaphragm to thetransmitter are through a path of solid continuity, as through the ringQ and the diaphragm D, the transmitter is put into communication withthe receiver just as effectively, for all practical purposes, as it iswhen it makes its contact directly with the receiver-diapln'agm. All ofthe articulate vibrations of the receiver-diaphragm are passed to thetransmitter, whereas by reason of the air separation between thevibrator and the diaphragm the inarticulate disturbances of thetransmitter are not communicated to the receiver. Thesecurement of thediaphragm D leaves a circumferential clearance which is not air-tight,so that the pressure balance between the air in the cushion G and thesurrounding atmosphere is maintained. 4

One feature which I regard as practically of great importance is theindependent adjustability of the receiver and transmitter members of therelay. As these two members are separated by a layer or cushion of air,it is quite obvious that the adjustment of one can be carried onentirely independently of the other, whereas in those instruments whosestructure involves mechanical contact or other mechanical connectionbetween the receiving and transmitting members of the relay the pro )eradjustment of one is very liable to affect t e adjustment of the other,and very nice compromises of adjustment have consequently to be resortedto. Moreover, the vibrating portion of the relay, which is set in motionin the magnetic field by the undulations of the current to be relayed,is entirely relieved of the load or restraint of thetransmitting-microphone or other transmitting device.

With respect to the transmission of. articulate speech as yet noinstrument has attained such perfection as the mierophonic transmitter.This transmitter in the usual commercial solid back form is providedwith its diaphragm for the reception of articulate sound-waves. In myimproved relay I employ just such a transmitter and subject it toconditions which closely resemble, if they do not exactly reproduce, theusual conditions presentwhen a person speaks to the microphonictransmitter. The vibrator of the receiver reproduces with accuracy thearticulate sound-waves emitted by the human voice into a distanttransmitter, and the receiver vibrator or diaphragm emits'thisarticulate vibration, setting the objects immediately in contact with itinto exactly similar undulations. The transmitter vibrator or diaphragmis subjected to the soundwaves which impinge upon it as effectively aswhen it is spoken to in the ordinary way. where, as in the instrumentdescribed in my patent aforesaid,,a relay-station is provided with aninstrument which enhances the force and amplitude of the articulatevibrations of loudly, the vibrator of such a relay is enabled thetelephonic circuit, so that the receiver of the relay mav speak not onlyintelligibly but to speak to. the vibrator of a transmitter with exactlythe same force and ell'ect as though the person originally sending themessage spoke directly into this transmitter.

,What I claim, and desire to secure by Letters Patent, is-

1. In a telephonic relay, a receiver, its diaphragm, a vibrator opposedto the receiverdiaphragm, an air layer between the vibrator anddiaphragm, in free communication with the circumambient atmosphere, atransmitter in connection with the vibrator, and continuous solid soundtransmitting connections betweenthe vibrator and the diaphr 1n.

2. n a telephonic relay, a receiver, its diaphra m, a vibrator op usedto the receiverdiap ragm and space therefrom, a transmitter inconnection with the vibrator, and a close metallic connection betweenthe .vibrator and the diaphra m.

3. In a telephonic relay, a receiver, its diaphragm, a vibrator op osedto the receiverdiaphragm and space therefrom, a transmitter inconnection with the vibrator, and a close metallie'connection betweenthe vibrator and the diaphragm at the margin of the latter, to insuresound communication and to permit mutually independent 'adjust-. ment ofthe transmitter and receiver, and means to adjust the transmitterindependently of the receiver. 4. In a telephonic repeater, thecombination of a receiving instrument and a transmitter, each providedwith a dia hragm, the diaphragms arranged arallel an opposed to eaeother, separated y an intervening layer of air which is in freecommunication with the surrounding atmosphere, the transverse area ofsaid air layer being substantially at least coequal with the area of thesmaller diaphragm, and solid sound-transmitting connections from theedge ofone diaphragm to the edge of the other.

5. In a telephonic repeater, the combination of .a receivim instrumentand a transmitter, each provided with a diaphragm, the

diaphragms parallel and opposed to each other separated by anintervening layer of air whic is in free communication with thesurrounding atmosphere, the transverse area of said air la er beingsubstansma er diaphragm, and solid sound-transmitting connections fromthe edge of one diaphragm to the edge of the other, and means to adjustthe receiver and the transmitter independently.

6.In a telephonic repeater, the combination of a receiving instrumentand a trans-. mitter, each(provided with a diaphragm, thetransmitteriaphragm of larger effective superficial area than that ofthe receiver, and a solid sound-transmitting connector which bears uponthe periphery of the receiver-diaphragm and upon thetransmitter-diaphragm etween the eriphery and the center thereof.

7. In a te ephonic repeater, the combination of a receiver and atransmitter, each provided with a diaphragm, the transmitter diaphragmof substantially greater superficial area than that of the receiver, thetwo diaphragms separated by an intervening layer of air which is in freecommunication with the surrounding atmosphere, and a solidsoundtransmitting connector bearing upon the receiver-diaphragm at theperiphery thereof and upon the transmitter-diaphragm between theperiphery and center thereof.

8. In a telephonic repeater, the combination of a receiver and atransmitter, each pro vided with a diaphragm, the transmitter-diaphragmof su erfioially greaterarea than the re'ceiver-diap. ragm, the twodiaphra ms concentrically arranged and in paralle opposition, and a ringof solid sound-transmitting material interposed between the dia hragmsand bearin upon the periphery of the receiver-diap ragm and upon thetransmitterdia hragm at a region between the center an peripherythereof.

Signe by me at Boston, Massachusetts, this13th day of Jul 1905.

- 7 J0 N TROWBRIDGE. Witnessesz.

JOSEPH T. BRENNAN,

CHARLES D. WOODBERRY.

tiallfi at least coequal with the area of the

